This invention relates to cementing heads used for the introduction and separation of fluids in a well, such as the introduction and separation of a cement slurry. Specifically, the invention relates to plug containers, manifolds and quick-latch couplers. As is well known in the art, cementing plugs utilized to separate fluids passing through casing in a wellbore are often held in a plug container. Rather than opening the top of the casing to insert cementing plugs, a plug container is installed at the top of the casing. The plug container has flow lines attached thereto and may have a quick-latch coupler connected thereto, which can be utilized to attach the plug container to the casing. The plug container may also have a manifold attached thereto which directs fluid into the plug container. A typical prior art plug container is shown in Halliburton Sales and Service Catalog No. 39, page 3138. A typical manifold is shown in Halliburton Casing Sales Manual No. 820.00005, pg. 3-12. Prior art quick-latch couplers are shown in U.S. Pat. Nos. 4,524,998 and 4,613,161 assigned to the assignee herein, both of which are incorporated in their entirety herein by reference.
At the beginning of a typical cementing job, the well casing and the well borehole are usually filled with drilling mud. To reduce the contamination at the interface between drilling mud and the cement which is pumped into the well casing on top of the drilling mud, a bottom cementing plug is often pumped ahead of the cement slurry so that the interface between the cement slurry and the drilling mud already in the well casing is defined by the bottom cementing plug.
As the cement is pumped into the well casing, the bottom cementing plug is pumped down the well casing. The bottom plug serves the function of wiping mud from the walls of the casing ahead of the cement slurry reducing dilution of the cement slurry, and serves to minimize contamination of cement as it is being pumped down the casing string. To separate the displacing fluid used to push the cement slurry out the tubular string and up the annular space, a top cementing plug is placed in line and pushed down the string by the displacing fluid. Typically, the bottom cementing plug is loaded into the plug container prior to pumping cement, and the top cementing plug will be loaded after the bottom plug is released. There may be times when only one cementing plug is used. In those cases, the plug is released after the cement to push the slurry out the tubular string. If well conditions dictate, a multiple plug container may be used which allows both cementing plugs to be released when desired without opening the plug container. Whether a single or multiple plug container is used, it can either be a free-fall or manifold type plug container.
The manifold utilized with plug containers is typically connected to inlets in the side of the plug container and is valved so that fluid can be displaced ahead of and behind cementing plugs. Often, the plug container and manifold may be made up as much as thirty feet off the rig floor. Because of the size, shape and weight of the plug and manifold assembly, it is difficult, time consuming and sometimes dangerous to make up the plug container, manifold and casing. Thus, there is a need for shorter and lighter plug containers, and more compact manifolds which are more maneuverable and easier and safer to handle.
Short plug container length is also important where rigs have short bales leaving little vertical distance above the top of the casing in which to make up the plug container. It is also desirable on some occasions to provide a means for quickly connecting the plug container to a casing collar in some manner other than making a threaded connection to a casing collar. Coupling apparatus for quick connection are shown in U.S. Pat. Nos. 4,613,161 and 4,524,998. While such apparatus work well, there is still a need for a shorter, more compact coupling apparatus that is easy to assemble. The present invention provides compact plug containers and manifolds which make assembly easier and make the cementing head easier to handle, and also provides a compact, readily assembled coupling apparatus.
The present invention provides a cementing head which is compact, maneuverable and easily assemblable. The cementing head of the present invention includes a plug container having first, or upper and second, or lower fluid inlets oriented 90xc2x0 from a longitudinal central axis of the plug container and offset therefrom. Thus, fluid entering the plug container creates a flow vortex which will draw plugs in the container down into the casing string. A manifold may be connected to the plug container.
The manifold includes a first valve connected to the upper inlet of the plug container and a second valve connected to the lower inlet of the plug container. A first discharge tee is connected to the first valve and a second discharge tee is connected to the second valve. The first and second discharge tees are connected to one another with a closing nut which is preferably a one-piece closing nut. The closing nut will engage threads on the first and second discharge tees such that rotation of the closing nut in one direction will cause the discharge tees to move toward one another and tighten against a spacer disposed therebetween to create a fluid-tight connection. Rotation of the closing nut in a second direction will cause the space between the first and second tees to increase and loosen the seal against the spacer.
The first discharge tee may have a left-hand thread defined thereon and the second discharge tee may have a right-hand thread defined thereon. The closing nut will have corresponding left- and right-hand threads defined on corresponding first and second ends thereof to engage the first and second discharge tees. The manifold has a fluid inlet which can be connected to a fluid supply line, the valves in the manifold can be manipulated to direct flow to the upper or lower inlets of the plug container.
A multiple plug container is also disclosed. The multiple plug container of the present invention has a plug container body with sufficient length to hold a top and a bottom cementing plug. The multiple plug container of the present invention has only two fluid inlets. Thus, the manifold may be connected to the upper and lower fluid inlets such that the multiple plug container is a combination free-fall manifold plug container. In other words, the manifold can be manipulated such that flow is directed through the upper inlet in the plug container on top of the bottom plug. The top plug, however, is necessarily a free-fall plug. The inlets in the multiple plug container are oriented 90xc2x0 to the longitudinal central axis thereof and offset therefrom such that a flow vortex is created in the plug container body which will draw the top plug into the flow stream.
A coupling apparatus for connecting the plug container to a casing string is also provided. The coupling apparatus comprises a body having threads defined thereon and a bore defined therethrough. A seal is disposed in the bore and is designed to seal against the upper end of a casing received in the bore. A locking clamp is disposed about the body. The locking clamp has a radially inwardly extending lip at a lower end thereof.
The locking clamp comprises first and second arcuate clamp portions hingedly connected to one another and movable between open and closed positions. Each arcuately shaped clamp portion has the radially inwardly extending lip at a lower end thereof.
When the locking clamp is in the closed position, the lip is closely received about the outer diameter of the casing below the lower end of a casing collar attached to the upper end of the casing. The lip defines an upward facing annular surface which will engage a downward facing annular surface defined by the casing collar, which may be referred to as an enlarged diameter portion of the casing. Rotation of the clamp once it is in the closed position will cause the casing to move longitudinally relative to the body, and will cause an initial compression of the seal disposed in the bore of the body to increase. A limit ring is provided for limiting the opening movement of the arcuate clamp portions. A latch means is provided for latching the locking clamp in its open or closed positions.